The invention relates to an electric motor intended for use in high-temperature environments and having a stator, having a rotor which is arranged in a rotationally fixed manner on a shaft, having bearing plates which each have one bearing for the shaft, and having a tubular housing on whose end faces the bearing plates are mounted, with the housing being produced from a highly thermally conductive material.
Such electric motors are often used close to or on an internal combustion engine in motor vehicles, and are known from practice. The housing is in this case manufactured as a tube closed at the rear, for example from sheet steel. When the electric motor is used in high-temperature environments, the heat which is produced as a result of operation of the electric motor accumulates inside the housing. The bearing plates are therefore made of aluminum and dissipate the heat produced inside the electric motor to the tubular housing. The housing is thus used to dissipate the heat produced during operation of the electric motor, for example to a bodywork part or to a component of the internal combustion engine in the motor vehicle.
A disadvantageous feature of the known electric motor is that it is highly costly to manufacture. For example, the bearing plates of the known electric motor are first of all produced by die casting from aluminum. The holders for one of the bearings and a connection for the housing are then turned.
The invention is based on the problem of refining an electric motor of the type mentioned initially such that it can be manufactured particularly cost-effectively.
This problem is solved in that at least one of the bearing plates is made of plastic and has a heat dissipation plate on its end facing the rotor.
This refinement of the electric motor according to the invention leads to a major reduction in the material costs for the bearing plate, since the heat dissipation plate can be designed with considerably thinner walls than the aluminum bearing plate. Furthermore, the plastic for the bearing plate can be manufactured with particularly tight tolerances, so that there is no longer any need for costly reworking on lathes. The electric motor according to the invention can thus be manufactured particularly cost-effectively.
According to another advantageous development of the invention, the plastic bearing plate is subjected to a particularly low heat load if the heat dissipation plate is at a distance from the bearing plate in the region of the bearing.
According to another advantageous development of the invention, reliable heat transfer from the bearing of the bearing plate to the heat dissipation plate can easily be ensured if the heat dissipation plate is pressed against the bearing.
According to another advantageous development of the invention, the heat transfer from the bearing to the heat dissipation plate is further improved if the heat dissipation plate has a collar in the form of a sleeve for pressing against the bearing.
According to another advantageous development of the invention, heat produced inside the housing is reliably kept away from the bearing if the collar has a rim which faces radially inward and engages over the bearing. This rim is used as a cover for the bearing and can be continued to a point immediately in front of the shaft.
According to another advantageous development of the invention, reliable heat transfer from the heat dissipation plate to the tubular housing can easily be ensured if a circumferential rim of the heat dissipation plate is clamped axially between the bearing plate and the tubular housing.
The heat dissipation plate could, for example, be made of aluminum. However, according to another advantageous development of the invention, it is possible to ensure that the bearing is reliably and permanently pressed against the heat dissipation plate if the heat dissipation plate is made of copper. If the heat dissipation plate is made of copper and the bearing is made of steel, the two components have approximately the same coefficients of thermal expansion, so that the push fit of the components is not loaded by temperature fluctuations.
The heat dissipation plate could, for example, have an annular shape. However, according to another advantageous development of the invention, the heat dissipation plate has a particularly low weight if the collar, which is in the form of a sleeve, and that rim of the heat dissipation plate which is prestressed against the housing are connected to one another via webs. This also contributes to a further reduction in the material costs of the electric motor according to the invention.
According to another advantageous development of the invention, the plastic of the bearing plate can withstand particularly high temperatures if the plastic of the bearing plate hardens chemically.